How can I add items from a listbox to a list by clicking a button without any codebehind?

问题

I am new to MVVM, and also fairly new to WPF. As a matter of fact I started programming just a few months ago. MVVM is really dng my head in with the binding concept, and I have been trying for days now to just simply make an application that allows you to select an item from a listbx, and when you click on the add button the selected item should be saved in a new list. The second listbox displays the latest items added, and you can select an item and delete it by using another button. ususally I would go for the click event and decorate my codebehind with pretty little methods, but I really want to learn how to do all this by using bindings and no codebehind. I would be extremly happy for any help, and please remember that I am new to this and I really want to keep it as simple as possible :) with kind regards Daniela

<WrapPanel HorizontalAlignment="Center" Margin=" 10">
   <ListBox x:Name="Firstbox" 
            Width="100"
            ItemsSource="{Binding FoodList}"
            DisplayMemberPath="Name" >
   </ListBox>
   <Button Margin="10 >Select</Button>
   <ListBox Width="100"></ListBox>

private List _foodList;

    public List<FoodItem> FoodList
    {
        get { return _foodList; }
        set { _foodList = value; }
    }

    private List<FoodItem> _newFoodList;

    public List<FoodItem> NewFoodList
    {
        get { return _newFoodList; }
        set { _newFoodList = value; }
    }

    public MainViewModel()
    {
        InitializeCommands();
        GetFood();
    }
    private void GetFood()
    {
        FoodList = new List<FoodItem>()
        {
            new FoodItem() {Name="Applepie"}, 
            new FoodItem() {Name="Scones"}
        };
    }

回答1:

first, you need to replace the Lists with ObservableCollections, so that the UI can detect when new items are added.

Add a SelectedItem property to your ViewModel:

private FoodItem _selectedItem;
public FoodItem SelectedItem
{
    get { return _selectedItem;}
    set
    {
        _selectedItem = value;
        OnPropertyChanged("SelectedItem");
    }
}

bind the SelectedItem property of the 1st ListBox to this property:

<ListBox Width=" 100" x:Name="Firstbox"
         ItemsSource="{Binding FoodList}"
         DisplayMemberPath="Name"
         SelectedItem="{Binding SelectedItem}" />

bind your 2nd ListBox to the NewFoodList property

create a command in your ViewModel:

private DelegateCommand _addItemCommand;
public ICommand AddItemCommand
{
    get
    {
        if (_addItemCommand == null)
        {
            _addItemCommand = new DelegateCommand(AddItem);
        }
        return _addItemCommand;
    }
}

void AddItem()
{
    if (SelectedItem != null)
        NewFoodList.Add(SelectedItem);
}

And finally, bind the button's Command property to the AddItemCommand property:
```
<Button Margin="10" Command="{Binding AddItemCommand}" >Select</Button>
```

来源：https://stackoverflow.com/questions/8114447/how-can-i-add-items-from-a-listbox-to-a-list-by-clicking-a-button-without-any-co

标签

wpf

mvvm

listbox